Recently, several types of Distributed Generators (DGs) have been connected together to form a small power system called a micro grid (MG). MG usually operates in normal connecting mode and is connected to the main grid. If a fault occurs in the main grid, MG will transfer immediately to the islanding mode. This paper developed a complete model which can simulate, in detail, the dynamic performance of the MG during and subsequent to islanding occurrence. The developed model is used to investigate the effect of using storage batteries for enhancing MG dynamic performance during all modes. Two cases are studied, the first case discusses the effect of the islanding process on the frequency, voltages and active powers of all micro sources when there are no storage batteries installed inside the MG. The second studied case investigates the effect of islanding occurrence on the MG performance when MG is equipped with two storage batteries. In the two studied cases, wind speed and irradiance vary continuously. Results proved that the existence of storage batteries led to dramatic improvement in the dynamic performance of the MG during subsequent islanding occurrence. Also, MG performance, when exposed to a severe disturbance, led to an unacceptable frequency drop is studied and load shedding strategy activation during this situation is also highlighted.